Electrosurgical system with suction control, apparatus, system and method

ABSTRACT

System and method for selectively applying electrical energy to structures within or on the surface of a patient&#39;s body and controlling the flow of an electrically conductive fluid from the application site to provide or maintain a desired operating condition of the electrosurgical device. An electrosurgical probe is in communication with a fluid transport apparatus through a fluid transport lumen having an opening at an end proximate the application site and disposed proximate the electrosurgical probe. A controller in communication with the fluid transport apparatus provides control signals to the fluid transport apparatus in response to at least one operating parameter associated with the system. Based on the received control signals, the fluid transport apparatus adjusts a flow rate of the electrically conductive fluid at the application site through the fluid transport lumen in response to at least one operating parameter associated with the system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/457,654 filed Apr. 27, 2012, which is a divisional of U.S.application Ser. No. 11/969,283 filed Jan. 4, 2008, which claims thebenefit of U.S. Provisional Application No. 60/883,698, filed Jan. 5,2007, all of which are incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of electrosurgeryand, more particularly, to surgical devices and methods which employhigh frequency voltage to cut and ablate tissue and utilize suction toremove the ablated tissue.

BACKGROUND

The field of electrosurgery includes a number of loosely relatedsurgical techniques which have in common the application of electricalenergy to modify the structure or integrity of patient tissue.Electrosurgical procedures usually operate through the application ofvery high frequency currents to cut or ablate tissue structures, wherethe operation can be monopolar or bipolar. Monopolar techniques rely onexternal grounding of the patient, where the surgical device definesonly a single electrode pole. Bipolar devices comprise both electrodesfor the application of current between their surfaces.

Electrosurgical procedures and techniques are particularly advantageoussince they generally reduce patient bleeding and trauma associated withcutting operations. Current electrosurgical device and procedures,however, suffer from a number of disadvantages. For example, monopolardevices generally direct electric current along a defined path from theexposed or active electrode through the patient's body to the returnelectrode, which is externally attached to a suitable location on thepatient. This creates the potential danger that the electric currentwill flow through undefined paths in the patient's body, therebyincreasing the risk of unwanted electrical stimulation to portions ofthe patient's body. In addition, since the defined path through thepatient's body has a relatively high impedance (because of the largedistance or resistivity of the patient's body), large voltagedifferences must typically be applied between the return and activeelectrodes in order to generate a current suitable for ablation orcutting of the target tissue. This current, however, may inadvertentlyflow along body paths having less impedance than the defined electricalpath, which will substantially increase the current flowing throughthese paths, possibly causing damage to or destroying tissue along andsurrounding this pathway.

Bipolar electrosurgical devices have an inherent advantage overmonopolar devices because the return current path does not flow throughthe patient. In bipolar electrosurgical devices, both the active andreturn electrode are typically exposed so that they may both contacttissue, thereby providing a return current path from the active to thereturn electrode through the tissue. One drawback with thisconfiguration, however, is that the return electrode may cause tissuedesiccation or destruction at its contact point with the patient'stissue. In addition, the active and return electrodes are typicallypositioned close together to ensure that the return current flowsdirectly from the active to the return electrode. The close proximity ofthese electrodes generates the danger that the current will short acrossthe electrodes, possibly impairing the electrical control system and/ordamaging or destroying surrounding tissue.

The use of electrosurgical procedures (both monopolar and bipolar) inelectrically conductive environments can be further problematic. Forexample, many arthroscopic procedures require flushing of the region tobe treated with isotonic saline (also referred to as normal saline),both to maintain an isotonic environment and to keep the field ofviewing clear. The presence of saline, which is a highly conductiveelectrolyte, can also cause shorting of the electrosurgical electrode inboth monopolar and bipolar modes. Such shorting causes unnecessaryheating in the treatment environment and can further cause non-specifictissue destruction.

Many surgical procedures, such as oral, laparoscopic and open surgicalprocedures, are not performed with the target tissue submerged under anirrigant. In laparoscopic procedures, such as the resection of the gallbladder from the liver, for example, the abdominal cavity is pressurizedwith carbon dioxide (pneumoperitoneum) to provide working space for theinstruments and to improve the surgeon's visibility of the surgicalsite. Other procedures, such as the ablation of muscle or gingiva tissuein the mouth, the ablation and necrosis of diseased tissue, or theablation of epidermal tissue, are also typically performed in a “dry”environment or field (i.e., not submerged under an electricallyconducting irrigant).

Present electrosurgical techniques used for tissue ablation also sufferfrom an inability to control the depth of necrosis in the tissue beingtreated. Most electrosurgical devices rely on creation of an electricarc between the treating electrode and the tissue being cut or ablatedto cause the desired localized heating. Such arcs, however, often createvery high temperatures causing a depth of necrosis greater than 500 μm,frequently greater than 800 μm, and sometimes as great as 1700 μm. Theinability to control such depth of necrosis is a significantdisadvantage in using electrosurgical techniques for tissue ablation,particularly in arthroscopic procedures for ablating and/or reshapingfibrocartilage, articular cartilage, meniscal tissue, and the like.

In an effort to overcome at least some of these limitations ofelectrosurgery, laser apparatus have been developed for use inarthroscopic and other procedures. Lasers do not suffer from electricalshorting in conductive environments, and certain types of lasers allowfor very controlled cutting with limited depth of necrosis. Despitethese advantages, laser devices suffer from their own set ofdeficiencies. In the first place, laser equipment can be very expensivebecause of the costs associated with the laser light sources. Moreover,those lasers which permit acceptable depths of necrosis (such as eximerlasers, erbium:YAG lasers, and the like) provide a very low volumetricablation rate, which is a particular disadvantage in cutting andablation of fibrocartilage, articular cartilage, and meniscal tissue.The holmium:YAG and Nd:YAG lasers provide much higher volumetricablation rates, but are much less able to control depth of necrosis thanare the slower laser devices. The CO2 lasers provide high rate ofablation and low depth of tissue necrosis, but cannot operate in aliquid-filled cavity.

For these and other reasons, improved systems and methods are desiredfor the electrosurgical ablation and cutting of tissue. These systemsand methods should be capable of selectively cutting and ablating tissueand other body structures in electrically conductive environments, suchas regions filled with blood or irrigated with electrically conductivesolutions, such as isotonic saline, and in relatively dry environments,such as those encountered in oral, dermatological, laparoscopic,thoracosopic and open surgical procedures. Such apparatus and methodsshould be able to perform cutting and ablation of tissues, whilelimiting the depth of necrosis and limiting the damage to tissueadjacent to the treatment site.

The assignee of the present invention developed Coblation® technology.Coblation® technology involves the application of a high frequencyvoltage difference between one or more active electrode(s) and one ormore return electrode(s) to develop high electric field intensities inthe vicinity of the target tissue in order to treat said tissue. Thehigh electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize an electricallyconductive fluid over at least a portion of the active electrode(s) inthe region between the tip of the active electrode(s) and the targettissue. The electrically conductive fluid may be a liquid or gas, suchas isotonic saline, blood, extracelluar or intracellular fluid,delivered to, or already present at, the target site, or a viscousfluid, such as a gel, applied to the target site.

The electrosurgical devices described above may incorporate a suctionlumen to carry away blood, tissue or other material from the treatmentsite. Presently available devices that utilize suction typically accessvacuum pressure from a surgical vacuum source that is self-regulated tomaintain a pre-set vacuum pressure. One problem associated with suchsystems is that the flow of liquid, gas and/or tissue particles in thevicinity of the treatment end of device may negatively affect theefficacy of such electrosurgical devices.

SUMMARY OF THE INVENTION

The present invention provides a system and method for selectivelyapplying electrical energy to structures within or on the surface of apatient's body and controlling flow through an associated suctionapparatus to remove the ablated tissue. The system and method allow thesurgical team to perform electrosurgical interventions, such as ablationand cutting of body structures, while controlling the suction flow rateaccording to certain operating parameters in order to provide ormaintain a desired operating condition of the electrosurgical device.The system and method of the present invention are useful for surgicalprocedures in relatively dry environments, such as treating and shapinggingiva, for tissue dissection, e.g., separation of gall bladder fromthe liver, ablation and necrosis of diseased tissue, such as fibroidtumors, and dermatological procedures involving surface tissue ablationon the epidermis, such as scar or tattoo removal, tissue rejuvenationand the like. The present invention may also be useful in electricallyconducting environments, such as arthroscopic or cystoscopic surgicalprocedures. In addition, the present invention is useful for canalizingor boring channels or holes through tissue, such as the ventricular wallof the heart during transmyocardial revascularization procedures.

The methods of the present invention may include positioning anelectrosurgical probe adjacent the target tissue so that at least oneactive electrode is brought into close proximity to the target site. Areturn electrode is positioned within an electrically conducting liquid,such as isotonic saline, to generate a current flow path between thetarget site and the return electrode. High frequency voltage is thenapplied between the active and return electrode through the current flowpath created by the electrically conducting liquid in either a bipolaror monopolar manner. One or more operating parameters of the electricalprobe or voltage generator are preferably monitored and used to controlthe operation of an associated suction apparatus. The probe may then betranslated, reciprocated or otherwise manipulated to cut the tissue oreffect the desired depth of ablation.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the electrosurgical system including anelectrosurgical probe, an electrically conducting liquid supply, asuction apparatus and an electrosurgical power supply constructed inaccordance with the principles of the present invention;

FIGS. 2A and 2B illustrate a probe having a plurality of electrodeterminals spaced-apart over an electrode array surface;

FIG. 3 illustrates an embodiment of a probe where the distal portion ofshaft is bent;

FIG. 4 illustrates an embodiment of a including a separate liquid supplyinstrument;

FIG. 5 illustrates the design of a probe include an active electrodewith a ring-shaped geometry;

FIG. 6A-6C illustrate the design of a probe include an screen-typeactive electrode;

FIG. 7 illustrates a schematic view of an electrosurgical system suctionapparatus controller; and

FIG. 8 illustrates a schematic view of an electrosurgical systemaccording to teachings of the present disclosure.

DETAILED DESCRIPTION

Before the present invention is described in detail, it is to beunderstood that this invention is not limited to particular variationsset forth herein as various changes or modifications may be made to theinvention described and equivalents may be substituted without departingfrom the spirit and scope of the invention. As will be apparent to thoseof skill in the art upon reading this disclosure, each of the individualembodiments described and illustrated herein has discrete components andfeatures which may be readily separated from or combined with thefeatures of any of the other several embodiments without departing fromthe scope or spirit of the present invention. In addition, manymodifications may be made to adapt a particular situation, material,composition of matter, process, process act(s) or step(s) to theobjective(s), spirit or scope of the present invention. All suchmodifications are intended to be within the scope of the claims madeherein.

Methods recited herein may be carried out in any order of the recitedevents which is logically possible, as well as the recited order ofevents. Furthermore, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the invention. Also, it iscontemplated that any optional feature of the inventive variationsdescribed may be set forth and claimed independently, or in combinationwith any one or more of the features described herein.

All existing subject matter mentioned herein (e.g., publications,patents, patent applications and hardware) is incorporated by referenceherein in its entirety except insofar as the subject matter may conflictwith that of the present invention (in which case what is present hereinshall prevail). The referenced items are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such material by virtue of prior invention.

Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin the appended claims, the singular forms “a,” “an,” “said” and “the”include plural referents unless the context clearly dictates otherwise.It is further noted that the claims may be drafted to exclude anyoptional element. As such, this statement is intended to serve asantecedent basis for use of such exclusive terminology as “solely,”“only” and the like in connection with the recitation of claim elements,or use of a “negative” limitation. Last, it is to be appreciated thatunless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

The systems of the present invention may be configured to address anyapplication wherein a suction system may be utilized in conjunction withan electrosurgical device for treating tissue. The treatment device ofthe present invention may have a variety of configurations as describedabove. However, one variation of the invention employs a treatmentdevice using Coblation® technology.

As stated above, the assignee of the present invention developedCoblation® technology. Coblation® technology involves the application ofa high frequency voltage difference between one or more activeelectrode(s) and one or more return electrode(s) to develop highelectric field intensities in the vicinity of the target tissue. Thehigh electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize an electricallyconductive fluid over at least a portion of the active electrode(s) inthe region between the tip of the active electrode(s) and the targettissue. The electrically conductive fluid may be a liquid or gas, suchas isotonic saline, blood, extracelluar or intracellular fluid,delivered to, or already present at, the target site, or a viscousfluid, such as a gel, applied to the target site.

When the conductive fluid is heated enough such that atoms vaporize offthe surface faster than they recondense, a gas is formed. When the gasis sufficiently heated such that the atoms collide with each othercausing a release of electrons in the process, an ionized gas or plasmais formed (the so-called “fourth state of matter”). Generally speaking,plasmas may be formed by heating a gas and ionizing the gas by drivingan electric current through it, or by shining radio waves into the gas.These methods of plasma formation give energy to free electrons in theplasma directly, and then electron-atom collisions liberate moreelectrons, and the process cascades until the desired degree ofionization is achieved. A more complete description of plasma can befound in Plasma Physics, by R. J. Goldston and P. H. Rutherford of thePlasma Physics Laboratory of Princeton University (1995), the completedisclosure of which is incorporated herein by reference.

As the density of the plasma or vapor layer becomes sufficiently low(i.e., less than approximately 1020 atoms/cm3 for aqueous solutions),the electron mean free path increases to enable subsequently injectedelectrons to cause impact ionization within the vapor layer. Once theionic particles in the plasma layer have sufficient energy, theyaccelerate towards the target tissue. Energy evolved by the energeticelectrons (e.g., 3.5 eV to 5 eV) can subsequently bombard a molecule andbreak its bonds, dissociating a molecule into free radicals, which thencombine into final gaseous or liquid species. Often, the electrons carrythe electrical current or absorb the radio waves and, therefore, arehotter than the ions. Thus, the electrons, which are carried away fromthe tissue towards the return electrode, carry most of the plasma's heatwith them, allowing the ions to break apart the tissue molecules in asubstantially non-thermal manner.

By means of this molecular dissociation (rather than thermal evaporationor carbonization), the target tissue structure is volumetrically removedthrough molecular disintegration of larger organic molecules intosmaller molecules and/or atoms, such as hydrogen, oxygen, oxides ofcarbon, hydrocarbons and nitrogen compounds. This moleculardisintegration completely removes the tissue structure, as opposed todehydrating the tissue material by the removal of liquid within thecells of the tissue and extracellular fluids, as is typically the casewith electrosurgical desiccation and vaporization. A more detaileddescription of this phenomena can be found in commonly assigned U.S.Pat. No. 5,697,882, the complete disclosure of which is incorporatedherein by reference.

In some applications of the Coblation® technology, high frequency (RF)electrical energy is applied in an electrically conducting mediaenvironment to shrink or remove (i.e., resect, cut, or ablate) a tissuestructure and to seal transected vessels within the region of the targettissue. Coblation® technology is also useful for sealing larger arterialvessels, e.g., on the order of about 1 mm in diameter. In suchapplications, a high frequency power supply is provided having anablation mode, wherein a first voltage is applied to an active electrodesufficient to effect molecular dissociation or disintegration of thetissue, and a coagulation mode, wherein a second, lower voltage isapplied to an active electrode (either the same or a differentelectrode) sufficient to heat, shrink, and/or achieve hemostasis ofsevered vessels within the tissue.

The amount of energy produced by the Coblation® device may be varied byadjusting a variety of factors, such as: the number of activeelectrodes; electrode size and spacing; electrode surface area;asperities and sharp edges on the electrode surfaces; electrodematerials; applied voltage and power; current limiting means, such asinductors; electrical conductivity of the fluid in contact with theelectrodes; density of the fluid; and other factors. Accordingly, thesefactors can be manipulated to control the energy level of the excitedelectrons. Since different tissue structures have different molecularbonds, the Coblation® device may be configured to produce energysufficient to break the molecular bonds of certain tissue butinsufficient to break the molecular bonds of other tissue. For example,fatty tissue (e.g., adipose) has double bonds that require an energylevel substantially higher than 4 eV to 5 eV (typically on the order ofabout 8 eV) to break. Accordingly, the Coblation® technology generallydoes not ablate or remove such fatty tissue; however, it may be used toeffectively ablate cells to release the inner fat content in a liquidform. Of course, factors may be changed such that these double bonds canalso be broken in a similar fashion as the single bonds (e.g.,increasing voltage or changing the electrode configuration to increasethe current density at the electrode tips). A more complete descriptionof this phenomena can be found in commonly assigned U.S. Pat. Nos.6,355,032; 6,149,120 and 6,296,136, the complete disclosures of whichare incorporated herein by reference.

The active electrode(s) of a Coblation® device may be supported withinor by an inorganic insulating support positioned near the distal end ofthe instrument shaft. The return electrode may be located on theinstrument shaft, on another instrument or on the external surface ofthe patient (i.e., a dispersive pad). The proximal end of theinstrument(s) will include the appropriate electrical connections forcoupling the return electrode(s) and the active electrode(s) to a highfrequency power supply, such as an electrosurgical generator.

A more detailed discussion of applications and devices using Coblation®technology may be found in, for example, U.S. Pat. Nos. 5,697,882;6,190,381; 6,282,961; 6,296,638; 6,482,201; 6,589,239; 6,746,447;6,929,640; 6,949,096 and 6,991,631, and U.S. patent application Ser. No.10/713,643, each of which is incorporated herein by reference.

In one example of a Coblation® device for use with the presentembodiments, the return electrode of the device is typically spacedproximally from the active electrode(s) a suitable distance to avoidelectrical shorting between the active and return electrodes in thepresence of electrically conductive fluid. In many cases, the distaledge of the exposed surface of the return electrode is spaced about 0.5mm to 25 mm from the proximal edge of the exposed surface of the activeelectrode(s), preferably about 1.0 mm to 5.0 mm. Of course, thisdistance may vary with different voltage ranges, conductive fluids, anddepending on the proximity of tissue structures to active and returnelectrodes. The return electrode will typically have an exposed lengthin the range of about 1 mm to 20 mm.

A Coblation® treatment device for use in the present embodiments may usea single active electrode or an array of active electrodes spaced aroundthe distal surface of a catheter or probe. In the latter embodiment, theelectrode array usually includes a plurality of independentlycurrent-limited and/or power-controlled active electrodes to applyelectrical energy selectively to the target tissue while limiting theunwanted application of electrical energy to the surrounding tissue andenvironment resulting from power dissipation into surroundingelectrically conductive fluids, such as blood, normal saline, and thelike. A single active electrode (or one of a multiple electrodes) mayinclude a screen or mesh type electrode with multiple apertures sized topermit fluid to flow therethrought. The active electrodes may beindependently current-limited by isolating the terminals from each otherand connecting each terminal to a separate power source that is isolatedfrom the other active electrodes. Alternatively, the active electrodesmay be connected to each other at either the proximal or distal ends ofthe catheter to form a single wire that couples to a power source.

In one configuration, each individual active electrode in the electrodearray is electrically insulated from all other active electrodes in thearray within the instrument and is connected to a power source which isisolated from each of the other active electrodes in the array or tocircuitry which limits or interrupts current flow to the activeelectrode when low resistivity material (e.g., blood, electricallyconductive saline irrigant or electrically conductive gel) causes alower impedance path between the return electrode and the individualactive electrode. The isolated power sources for each individual activeelectrode may be separate power supply circuits having internalimpedance characteristics which limit power to the associated activeelectrode when a low impedance return path is encountered. By way ofexample, the isolated power source may be a user selectable constantcurrent source. In this embodiment, lower impedance paths willautomatically result in lower resistive heating levels since the heatingis proportional to the square of the operating current times theimpedance. Alternatively, a single power source may be connected to eachof the active electrodes through independently actuatable switches, orby independent current limiting elements, such as inductors, capacitors,resistors and/or combinations thereof. The current limiting elements maybe provided in the instrument, connectors, cable, controller, or alongthe conductive path from the controller to the distal tip of theinstrument. Alternatively, the resistance and/or capacitance may occuron the surface of the active electrode(s) due to oxide layers which formselected active electrodes (e.g., titanium or a resistive coating on thesurface of metal, such as platinum).

The Coblation® device is not limited to electrically isolated activeelectrodes, or even to a plurality of active electrodes. For example,the array of active electrodes may be connected to a single lead thatextends through the catheter shaft to a power source of high frequencycurrent.

The voltage difference applied between the return electrode(s) and theactive electrode(s) will be at high or radio frequency, typicallybetween about 5 kHz and 20 MHz, usually being between about 30 kHz and2.5 MHz, preferably being between about 50 kHz and 500 kHz, often lessthan 350 kHz, and often between about 100 kHz and 200 kHz. In someapplications, applicant has found that a frequency of about 100 kHz isuseful because the tissue impedance is much greater at this frequency.In other applications, such as procedures in or around the heart or headand neck, higher frequencies may be desirable (e.g., 400-600 kHz) tominimize low frequency current flow into the heart or the nerves of thehead and neck.

The RMS (root mean square) voltage applied will usually be in the rangefrom about 5 volts to 1000 volts, preferably being in the range fromabout 10 volts to 500 volts, often between about 150 volts to 400 voltsdepending on the active electrode size, the operating frequency and theoperation mode of the particular procedure or desired effect on thetissue (i.e., contraction, coagulation, cutting or ablation.)

Typically, the peak-to-peak voltage for ablation or cutting with asquare wave form will be in the range of 10 volts to 2000 volts andpreferably in the range of 100 volts to 1800 volts and more preferablyin the range of about 300 volts to 1500 volts, often in the range ofabout 300 volts to 800 volts peak to peak (again, depending on theelectrode size, number of electrons, the operating frequency and theoperation mode). Lower peak-to-peak voltages will be used for tissuecoagulation, thermal heating of tissue, or collagen contraction and willtypically be in the range from 50 to 1500, preferably 100 to 1000 andmore preferably 120 to 400 volts peak-to-peak (again, these values arecomputed using a square wave form). Higher peak-to-peak voltages, e.g.,greater than about 800 volts peak-to-peak, may be desirable for ablationof harder material, such as bone, depending on other factors, such asthe electrode geometries and the composition of the conductive fluid.

As discussed above, the voltage is usually delivered in a series ofvoltage pulses or alternating current of time varying voltage amplitudewith a sufficiently high frequency (e.g., on the order of 5 kHz to 20MHz) such that the voltage is effectively applied continuously (ascompared with, e.g., lasers claiming small depths of necrosis, which aregenerally pulsed about 10 Hz to 20 Hz). In addition, the duty cycle(i.e., cumulative time in any one-second interval that energy isapplied) is on the order of about 50% for the present invention, ascompared with pulsed lasers which typically have a duty cycle of about0.0001%.

The preferred power source or generator of the present inventiondelivers a high frequency current selectable to generate average powerlevels ranging from several milliwatts to tens of watts per electrode,depending on the volume of target tissue being treated, and/or themaximum allowed temperature selected for the instrument tip. The powersource allows the user to select the voltage level according to thespecific requirements of a particular neurosurgery procedure, cardiacsurgery, arthroscopic surgery, dermatological procedure, ophthalmicprocedures, open surgery or other endoscopic surgery procedure. Forcardiac procedures and potentially for neurosurgery, the power sourcemay have an additional filter, for filtering leakage voltages atfrequencies below 100 kHz, particularly voltages around 60 kHz.Alternatively, a power source having a higher operating frequency, e.g.,300 kHz to 600 kHz may be used in certain procedures in which stray lowfrequency currents may be problematic. A description of one suitablepower source can be found in commonly assigned U.S. Pat. Nos. 6,142,992and 6,235,020, the complete disclosure of both patents are incorporatedherein by reference for all purposes.

The power source may be current limited or otherwise controlled so thatundesired heating of the target tissue or surrounding (non-target)tissue does not occur. In certain embodiments, current limitinginductors are placed in series with each independent active electrode,where the inductance of the inductor is in the range of 10 uH to 50,000uH, depending on the electrical properties of the target tissue, thedesired tissue heating rate and the operating frequency. Alternatively,capacitor-inductor (LC) circuit structures may be employed, as describedpreviously in U.S. Pat. No. 5,697,909, the complete disclosure of whichis incorporated herein by reference. Additionally, current-limitingresistors may be selected. Preferably, these resistors will have a largepositive temperature coefficient of resistance so that, as the currentlevel begins to rise for any individual active electrode in contact witha low resistance medium (e.g., saline irrigant or blood), the resistanceof the current limiting resistor increases significantly, therebyminimizing the power delivery from said active electrode into the lowresistance medium (e.g., saline irrigant or blood).

In certain embodiments of the present system, a suction lumen may beprovided with the electrosurgical device. The suction lumen ispreferably in communication with a suction source such as a suctionpump, and is also in communication with a suction opening positionedproximate to the treatment surface of the electrosurgical device. Aportion of the suction lumen may be located internally within theelectrosurgical device or may be attached to the exterior of theelectrosurgical device. The suction lumen preferably has a diametersized to effectively remove ablated tissue and other material away fromthe treatment site. A fluid supply lumen may also be provided. The fluidsupply lumen may utilized separate from the electrosurgical device ormay be integrated with the electrosurgical device (either on theexterior or within the interior of said device.)

The suction source may encompass any suitable fluid transport apparatus.In some embodiments the suction source may be a suction pump. Thesuction source may be a positive displacement pump such as, for example,a peristaltic pump. In some embodiments the suction source may comprisea vacuum pump and canister assembly such as may be provided via a walloutlet in a surgical suite.

Certain embodiments of the present disclosure may include a controllerdevice used to periodically receive data related to one or moreoperating parameters associated with the electrosurgical device orvoltage generator, and, responsive to the operating parameter data, sendcontrol signals to an associated suction source. The control signals mayoperate to activate the suction source in conjunction with the use ofthe electrosurgical device. In other embodiments, the control signalsmay be used to dynamically adjust fluid flow through the suction source,initiate fluid flow through the suction source, delay initiating fluidflow through the suction source, cease fluid flow through the suctionsource, decrease fluid flow through the suction source, incrementallyincrease or decrease fluid flow through the vacuum source, and/ormaintain a particular fluid flow through the suction source if theoperating parameters remain within a pre-selected value range. In otherembodiments, the control signals from the controller device maydynamically control the pressure at the suction source.

The input signals into the controller may preferably include any inputsignals indicative of operating conditions at the distal end of theelectrosurgical device. These may include, but are not limited to,operating parameters measured by a sensor within an electrosurgicalprobe, within a generator or within the suction lumen. Such operatingparameters my include, buy are not limited to, impedance, electriccurrent (including whether a treatment current has been initiated orstopper), peak electric current and mean electric current for a selectedperiod, peak electric current and RMS voltage for a selected period. Fordevices that may operate in more than one operating mode, such as anablation mode and a coagulation mode, the operating parameter may beassociated with signals indicating the operating mode of the device.

The embodiments of the present device provide a system and method forselectively applying electrical energy to a target location within or ona patient's body and removing tissue and other material from the targetlocation through a fluid transport lumen. In certain embodiments, theflow rate of tissue and associated fluids removed through the transportlumen may be controlled according to operating parameters associatedwith an electrosurgical probe or a voltage generator. The system andmethod may be utilized for the treatment of solid tissue or the like,particularly including gingival tissues and mucosal tissues located inthe mouth or epidermal tissue on the outer skin. In addition, tissueswhich may be treated by the system and method of the present inventioninclude tumors, abnormal tissues, and the like. The embodimentsdescribed herein may also be used for canalizing or boring channels orholes through tissue, such as the ventricular wall duringtransmyocardial revascularization procedures. It will be appreciatedthat the system and method can be applied equally well to proceduresinvolving other tissues of the body, as well as to other proceduresincluding open surgery, laparoscopic surgery, thoracoscopic surgery, andother endoscopic surgical procedures. Notably, the system and methoddescribed herein is particularly useful in procedures where the tissuesite is flooded or submerged with an electrically conducting fluid, suchas isotonic saline, e.g., arthroscopic surgery and the like.

In one embodiment, a single active electrode or an electrode arraydistributed over a distal contact surface of a probe may be used. Theelectrode array usually includes a plurality of independentlycurrent-limited and/or power-controlled electrode terminals to applyelectrical energy selectively to the target tissue while limiting theunwanted application of electrical energy to the surrounding tissue andenvironment resulting from power dissipation into surroundingelectrically conductive liquids, such as blood, normal saline, and thelike. The electrode terminals may be independently current-limited byusing isolating the terminals from each other and connecting eachterminal to a separate power source that is isolated from the otherelectrode terminals. Alternatively, the electrode terminals may beconnected to each other at either the proximal or distal ends of theprobe to form a single wire that couples to a power source.

The electrosurgical probe may comprise a shaft having a proximal end anda distal end which supports an active electrode. The shaft may assume awide variety of configurations, with the primary purpose being tomechanically support the active electrode and permit the treatingphysician to manipulate the electrode from a proximal end of the shaft.Usually, the shaft will be a narrow-diameter rod or tube, more usuallyhaving dimensions which permit it to be introduced into a body cavity,such as the mouth or the abdominal cavity, through an associated trocaror cannula in a minimally invasive procedure, such as arthroscopic,laparoscopic, thoracoscopic, and other endoscopic procedures. Thus, theshaft will typically have a length of at least 5 cm for oral proceduresand at least 10 cm, more typically being 20 cm, or longer for endoscopicprocedures. The shaft will typically have a diameter of at least 1 mmand frequently in the range from 1 to 10 mm. Of course, fordermatological procedures on the outer skin, the shaft may have anysuitable length and diameter that would facilitate handling by thesurgeon.

The shaft may be rigid or flexible, with flexible shafts optionallybeing combined with a generally rigid external tube for mechanicalsupport. Flexible shafts may be combined with pull wires, shape memoryactuators, and other known mechanisms for effecting selective deflectionof the distal end of the shaft to facilitate positioning of theelectrode array. The shaft will usually include a plurality of wires orother conductive elements running axially therethrough to permitconnection of the electrode array to a connector at the proximal end ofthe shaft. Specific shaft designs will be described in detail inconnection with the figures hereinafter.

The circumscribed area of the electrode array may be in the range from0.25 mm2 to 75 mm2, preferably from 0.5 mm2 to 40 mm2, and will usuallyinclude at least two isolated electrode terminals, more usually at leastfour electrode terminals, preferably at least six electrode terminals,and often 50 or more electrode terminals, disposed over the distalcontact surfaces on the shaft. By bringing the electrode array(s) on thecontact surface(s) in close proximity with the target tissue andapplying high frequency voltage between the array(s) and an additionalcommon or return electrode in direct or indirect contact with thepatient's body, the target tissue is selectively ablated or cut,permitting selective removal of portions of the target tissue whiledesirably minimizing the depth of necrosis to surrounding tissue. Inparticular, this invention provides a method and apparatus foreffectively ablating and cutting tissue which may be located in closeproximity to other critical organs, vessels or structures (e.g., teeth,bone) by simultaneously (1) causing electrically conducting liquid toflow between the common and active electrodes, (2) applying electricalenergy to the target tissue surrounding and immediately adjacent to thetip of the probe, (3) bringing the active electrode(s) in closeproximity with the target tissue using the probe itself, (4) controllingthe fluid flow through or pressure within an associated suction sourceand (5) optionally moving the electrode array axially and/ortransversely over the tissue.

Electrosurgical probes according to the present invention may include asingle active electrode or two or more active electrodes. In someembodiments the active electrodes may be formed around a suctionopening. Other embodiments may include a screen electrode with multipleapertures formed therein to allow fluid to flow therethrough. Oneembodiment includes at least one ring-shaped electrode with an openingformed therein through with a suction opening may be provided. Theactive electrode or electrodes may be provided in any suitable numberand configuration (including placement with respect to the suction lumenopening) for treating tissue.

The tip region of the probe may be composed of many independentelectrode terminals designed to deliver electrical energy in thevicinity of the tip. The selective application of electrical energy tothe target tissue is achieved by connecting each individual electrodeterminal and the common electrode to a power source having independentlycontrolled or current limited channels. The common electrode may be atubular member of conductive material proximal to the electrode array atthe tip which also serves as a conduit for the supply of theelectrically conducting liquid between the active and common electrodes.The application of high frequency voltage between the common electrodeand the electrode array results in the generation of high electric fieldintensities at the distal tips of the electrodes with conduction of highfrequency current from each individual electrode terminal to the commonelectrode. The current flow from each individual electrode terminal tothe common electrode is controlled by either active or passive means, ora combination thereof, to deliver electrical energy to the target tissuewhile minimizing energy delivery to surrounding (non-target) tissue andany conductive fluids which may be present (e.g., blood, electrolyticirrigants such as saline, and the like).

In a preferred aspect, this invention takes advantage of the differencesin electrical resistivity between the target tissue (e.g., gingiva,muscle, fascia, tumor, epidermal, heart or other tissue) and thesurrounding conductive liquid (e.g., isotonic saline irrigant). By wayof example, for any selected level of applied voltage, if the electricalconduction path between the common electrode and one of the individualelectrode terminals within the electrode array is isotonic salineirrigant liquid (having a relatively low electrical impedance), thecurrent control means connected to the individual electrode will limitcurrent flow so that the heating of intervening conductive liquid isminimized. On the other hand, if a portion of or all of the electricalconduction path between the common electrode and one of the individualelectrode terminals within the electrode array is gingival tissue(having a relatively higher electrical impedance), the current controlcircuitry or switch connected to the individual electrode will allowcurrent flow sufficient for the deposition of electrical energy andassociated ablation or electrical breakdown of the target tissue in theimmediate vicinity of the electrode surface.

The application of a high frequency voltage between the common or returnelectrode and the electrode array for appropriate time intervals effectsablation, cutting or reshaping of the target tissue. The tissue volumeover which energy is dissipated (i.e., a high voltage gradient exists)may be precisely controlled, for example, by the use of a multiplicityof small electrodes whose effective diameters range from about 2 mm to0.01 mm, preferably from about 1 mm to 0.05 mm, and more preferably fromabout 0.5 mm to 0.1 mm. Electrode areas for both circular andnon-circular terminals will have a contact area (per electrode) below 5mm2, preferably being in the range from 0.0001 mm2 to 1 mm2, and morepreferably from 0.005 mm2 to 0.5 mm2. The use of small diameterelectrode terminals increases the electric field intensity and reducesthe extent or depth of tissue necrosis as a consequence of thedivergence of current flux lines which emanate from the exposed surfaceof each electrode terminal. Energy deposition in tissue sufficient forirreversible damage (i.e., necrosis) has been found to be limited to adistance of about one-half to one electrode diameter. This is aparticular advantage over prior electrosurgical probes employing singleand/or larger electrodes where the depth of tissue necrosis may not besufficiently limited.

In some embodiments a high frequency voltage may be applied between theactive electrode surface and the return electrode to develop highelectric field intensities in the vicinity of the target tissue site.The high electric field intensities lead to electric field inducedmolecular breakdown of target tissue through molecular dissociation(rather than thermal evaporation or carbonization). In other words, thetissue structure is volumetrically removed through moleculardisintegration of complex organic molecules into non-viable atoms andmolecules, such as hydrogen, oxides of carbon, hydrocarbons and nitrogencompounds. This molecular disintegration completely removes the tissuestructure, as opposed to transforming the tissue material from a solidform directly to a vapor form, as is typically the case with ablation.

The high electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize the electricallyconducting liquid over at least a portion of the active electrode(s) inthe region between the distal tip of the active electrode and the targettissue. Since the vapor layer or vaporized region has a relatively highelectrical impedance, it increases the voltages differential between theactive electrode tip and the tissue and causes ionization within thevapor layer due to the presence of an ionizable species (e.g., sodiumwhen isotonic saline is the electrically conducting fluid). Thisionization, under optimal conditions, induces the discharge of energeticelectrons and photons from the vapor layer and to the surface of thetarget tissue. This energy may be in the form of energetic photons(e.g., ultraviolet radiation), energetic particles (e.g., electrons) ora combination thereof.

The necessary conditions for forming a vapor layer near the activeelectrode tip(s), ionizing the atom or atoms within the vapor layer andinducing the discharge of energy from plasma within the vapor layer willdepend on a variety of factors, such as: the number of electrodeterminals; electrode size and spacing; electrode surface area;asperities and sharp edges on the electrode surfaces; electrodematerials; applied voltage and power; current limiting means, such asinductors; electrical conductivity of the fluid in contact with theelectrodes; density of the fluid; and other factors. Based on initialexperiments, applicants believe that the ionization of atoms within thevapor layer produced in isotonic saline (containing sodium chloride)leads to the generation of energetic photons having wavelengths, by wayof example, in the range of 306 to 315 nanometers (ultraviolet spectrum)and 588 to 590 nanometers (visible spectrum). In addition, the freeelectrons within the ionized vapor layer are accelerated in the highelectric fields near the electrode tip(s). When the density of the vaporlayer (or within a bubble formed in the electrically conducting liquid)becomes sufficiently low (i.e., less than approximately 1020 atoms/cm3for aqueous solutions), the electron mean free path increases to enablesubsequently injected electrons to cause impact ionization within theseregions of low density (i.e., vapor layers or bubbles). Energy evolvedby the energetic electrons (e.g., 4 to 5 eV) can subsequently bombard amolecule and break its bonds, dissociating a molecule into freeradicals, which then combine into final gaseous or liquid species.

The photon energy produces photoablation through photochemical and/orphotothermal processes to disintegrate tissue thicknesses as small asseveral cell layers of tissue at the target site. This photoablation isa “cold” ablation, which means that the photon energy transfers verylittle heat to tissue beyond the boundaries of the region of tissueablated. The cold ablation provided by photon energy can be preciselycontrolled to only affect a thin layer of cells without heating orotherwise damaging surrounding or underlying cells. The depth ofnecrosis will be typically be about 0 to 400 microns and usually 10 to200 microns. Applicants believe that the “fragments” of disintegratedtissue molecules carry away much of the energy which is deposited on thesurface of the target tissue, thereby allowing molecular disintegrationof tissue to occur while limiting the amount of heat transfer to thesurrounding tissue.

In addition, other competing mechanisms may be contributing to theablation of tissue. For example, tissue destruction or ablation may alsobe caused by dielectric breakdown of the tissue structural elements orcell membranes from the highly concentrated intense electric fields atthe tip portions of the electrode(s). According to the teachings of thepresent invention, the active electrode(s) are sized and have exposedsurfaces areas which, under proper conditions of applied voltage, causethe formation of a vaporized region or layer over at least a portion ofthe surface of the active electrode(s). This layer or region ofvaporized electrically conducting liquid creates the conditionsnecessary for ionization within the vaporized region or layer and thegeneration of energetic electrons and photons. In addition, this layeror region of vaporized electrically conducting liquid provides a highelectrical impedance between the electrode and the adjacent tissue sothat only low levels of current flow across the vaporized layer orregion into the tissue, thereby minimizing joulean heating in, andassociated necrosis of, the tissue.

As discussed above, applicants have found that the density of theelectrically conducting liquid at the distal tips of the activeelectrodes should be less than a critical value to form a suitable vaporlayer. For aqueous solutions, such as water or isotonic saline, thisupper density limit is approximately 1020 atoms/cm3, which correspondsto about 3×10-3 grams/cm3. Applicant's also believe that once thedensity in the vapor layer reaches a critical value (e.g., approximately1020 atoms/cm3 for aqueous solutions), electron avalanche occurs. Thegrowth of this avalanche is retarded when the space charge generatedfields are on the order of the external field. Spatial extent of thisregion should be larger than the distance required for an electronavalanche to become critical and for an ionization front to develop.This ionization front develops and propagates across the vapor layer viaa sequence of processes occurring the region ahead of the front, viz,heat by electron injection, lowering of the local liquid density belowthe critical value and avalanche growth of the charged particleconcentration.

Electrons accelerated in the electric field within the vapor layer willapparently become trapped after one or a few scatterings. These injectedelectrons serve to create or sustain a low density region with a largemean free path to enable subsequently injected electrons to cause impactionization within these regions of low density. The energy evolved ateach recombination is on the order of half of the energy band gap (i.e.,4 to 5 eV). It appears that this energy can be transferred to anotherelectron to generate a highly energetic electron. This second, highlyenergetic electron may have sufficient energy to bombard a molecule tobreak its bonds, i.e., dissociate the molecule into free radicals.

The electrically conducting liquid should have a threshold conductivityin order to suitably ionize the vapor layer for the inducement ofenergetic electrons and photons. The electrical conductivity of thefluid (in units of milliSiemans per centimeter or mS/cm) will usually begreater than 0.2 mS/cm, preferably will be greater than 2 mS/cm and morepreferably greater than 10 mS/cm. In an exemplary embodiment, theelectrically conductive fluid is isotonic saline, which has aconductivity of about 17 mS/cm. The electrical conductivity of thechannel trailing the ionization front should be sufficiently high tomaintain the energy flow required to heat the liquid at the ionizationfront and maintain its density below the critical level. In addition,when the electrical conductivity of the liquid is sufficiently high,ionic pre-breakdown current levels (i.e., current levels prior to theinitiation of ionization within the vapor layer) are sufficient to alsopromote the initial growth of bubbles within the electrically conductingliquid (i.e., regions whose density is less than the critical density).

Asperities on the surface of the active electrode(s) may promotelocalized high current densities which, in turn, promote bubblenucleation at the site of the asperities whose enclosed density (i.e.,vapor density) is below the critical density to initiate ionizationbreakdown within the bubble. Hence, a specific configuration of thepresent invention creates regions of high current densities on the tipsof the electrode(s) (i.e., the surface of the electrode(s) which are toengage and ablate or cut tissue). Regions of high current densities canbe achieved via a variety of methods, such as producing sharp edges andcorners on the distal tips of the electrodes or vapor blasting,chemically etching or mechanically abrading the distal end faces of theactive electrodes to produce surface asperities thereon. Alternatively,the electrode terminals may be specifically designed to increase theedge/surface area ratio of the electrode terminals. For example, theelectrode terminal(s) may be hollow tubes having a distal,circumferential edge surrounding an opening. The terminals may be formedin an array as described above or in a series of concentric terminals onthe distal end of the probe. High current densities will be generatedaround the circumferential edges of the electrode terminals to promotenucleate bubble formation.

In some embodiments the active electrode(s) may be formed over a contactsurface on the shaft of the electrosurgical probe. The common (return)electrode surface will be recessed relative to the distal end of theprobe and may be recessed within the conduit provided for theintroduction of electrically conducting liquid to the site of the targettissue and active electrode(s). In the exemplary embodiment, the shaftwill be cylindrical over most of its length, with the contact surfacebeing formed at the distal end of the shaft. In the case of endoscopicapplications, the contact surface may be recessed since it helps protectand shield the electrode terminals on the surface while they are beingintroduced, particularly while being introduced through the workingchannel of a trocar channel or a viewing scope.

The area of the contact surface can vary widely, and the contact surfacecan assume a variety of geometries, with particular areas in geometriesbeing selected for specific applications. Active electrode contactsurfaces can have areas in the range from 0.25 mm2 to 50 mm2, usuallybeing from 1 mm2 to 20 mm2. The geometries can be planar, concave,convex, hemispherical, conical, linear “in-line” array or virtually anyother regular or irregular shape. Most commonly, the active electrode(s)will be formed at the distal tip of the electrosurgical probe shaft,frequently being planar, disk-shaped, or hemispherical surfaces for usein reshaping procedures or being linear arrays for use in cutting. Insome preferred embodiments the active electrode may be a screen or meshtype electrode. Alternatively or additionally, the active electrode(s)may be formed on lateral surfaces of the electrosurgical probe shaft(e.g., in the manner of a spatula), facilitating access to certain bodystructures in electrosurgical procedures.

During the surgical procedure, the distal end of the probe or the activeelectrode(s) will be maintained at a small distance away from the targettissue surface. This small spacing allows for the continual resupply ofelectrically conducting liquid into the interface between the activeelectrode(s) and the target tissue surface and removal of ablated tissueand other material through a fluid transport or suction lumen. Thecontinual resupply of the electrically conducting liquid and controlledremoval of ablated tissue and other material helps to ensure that thethin vapor layer will remain between active electrode(s) and the tissuesurface. Moreover, the condition of the vapor layer at the electrode(s)may be monitored, for example, by measuring impedance or electriccurrent at the treatment interface through sensors located in proximityto the probe. Depending on the status of the vapor layer conditionmeasured, the flow of fluid through the suction lumen may be dynamicallyadjusted through control of the suction apparatus in order to maintain astable vapor layer. For example, if the impedance at the treatmentinterface is detected to be above a preferred operating parameter, theflow of fluid through the suction lumen may be initiated or increased.Conversely, if instability in the vapor layer is detected throughmeasurement of an operating condition associated with electrosurgicalprobe, the flow of fluid through the fluid transport or suction lumenmay be decreased or, in some cases, completely ceased. In addition,dynamic movement of the active electrode(s) over the tissue site allowsthe electrically conducting liquid to cool the tissue surroundingrecently ablated areas to minimize thermal damage to this surroundingtissue. In some embodiments the active electrode(s) will be about 0.02to 2 mm from the target tissue and preferably about 0.05 to 0.5 mmduring the ablation process. One method of maintaining this space is totranslate and/or rotate the probe transversely relative to the tissue,i.e., a light brushing motion, to maintain a thin vaporized layer orregion between the active electrode and the tissue. Of course, ifcoagulation of a deeper region of tissue is necessary (e.g., for sealinga bleeding vessel imbedded within the tissue), it may be desirable topress the active electrode against the tissue to effect joulean heatingtherein.

Referring to the drawings in detail, wherein like numerals indicate likeelements, an electrosurgical system 11 is shown constructed according tothe principles of the present invention. Electrosurgical system 11generally comprises an electrosurgical probe 10 connected to a powersupply 28 for providing high frequency voltage to a target tissue and aliquid source 21 for supplying electrically conducting fluid 50 to probe10 via fluid supply conduit 15. Fluid supply conduit may include a valve17 for controlling fluid flow at the distal end thereof 14 and to wand10.

In an exemplary embodiment as shown in FIG. 1, electrosurgical probe 10includes an elongated shaft 13 which may be flexible or rigid, withflexible shafts optionally including support cannulas or otherstructures (not shown). Probe 10 includes a connector 19 at its proximalend and an array 12 of electrode terminals 58 disposed on the distal tipof shaft 13. As discussed above, the present invention may include avariety of electrode configurations that may be employed withelectrosurgical probe 10 (include embodiments with a single electrodesuch as a screen electrode or a screen electrode). A connecting cable 34has a handle 22 with a connector 20 which can be removably connected toconnector 19 of probe 10. The proximal portion of cable 34 has aconnector 26 to couple probe 10 to power supply 28. The electrodeterminals 58 are electrically isolated from each other and each of theterminals 58 is connected to an active or passive control network withinpower supply 28 by means of a plurality of individually insulatedconductors 42. Power supply 28 has a selection means 30 to change theapplied voltage level. Power supply 28 may also be referred to generallyas a “generator” herein. Power supply 28 also includes means forenergizing the electrodes 58 of probe 10 through the depression of apedal 39 in a foot pedal 37 positioned close to the user and isconnected to power supply 28 via cable 36. The foot pedal 37 may alsoinclude a second pedal (not shown) for remotely adjusting the energylevel applied to electrodes 58 or for selecting an alternate operatingmode.

Suction lumen 102 is in communication with the electrosurgical probe 10and with suction pump 100. Suction pump 100 is further in electricalcommunication with controller 104 via cable 106. Suction pump 100 mayencompass any suitable fluid transport apparatus. Suction pump 100 maycomprise a positive displacement pump such as, for example, aperistaltic pump. In some embodiments the suction pump 100 may comprisea vacuum pump and canister assembly such as may be provided via a walloutlet in a surgical suite.

As shown in the present embodiment, controller 104 may be associatedwith power supply 28 and may receive input regarding one or moreoperating parameters therefrom. It should be appreciated that thelocation of controller 104 may be altered within the present invention,and may alternatively be located within suction pump 100 or provided asan independent component. Controller 104 may also be disposed directlywithin probe 10. In certain embodiments, controller 104 may eitherreceive operating parameter input from a suitable senor or sensorswithin power supply 28 or probe 10. Controller 104 periodically receivesdata related to one or more operating parameters associated withelectrosurgical probe 10 or power supply 28.

The input received by controller 104 may preferably include any inputsignals indicative of operating conditions at the distal end of theelectrosurgical probe. These may include, but are not limited to,operating parameters measured by a sensor within an electrosurgicalprobe, within a generator or within the suction lumen. The presentembodiment shows the controller 104 receiving operating parameter datafrom power supply 28. Such operating parameters my include, but are notlimited to, impedance, electric current (including whether a treatmentcurrent has been initiated or stopper), peak electric current and meanelectric current for a selected period, peak electric current and RMSvoltage for a selected period. For devices that may operate in more thanone operating mode, such as an ablation mode and a coagulation mode, theoperating parameter may include the operating mode of the device.

In certain embodiments, the operating parameter input data received bycontroller 104 may be indicative of operating conditions at the distalend of probe 10. For example, the impedance at the distal end of probe10 may be an operating parameter that is measured by an electrosurgicalprobe sensor (not shown) and transmitted to controller 104 forprocessing. Typically, the impedance at electrode terminals 58 increaseswhen a plasma field is established at that location, whereas theimpedance is found to decrease as the plasma field becomes unstable.Therefore, a measurement of impedance may provide operating parameterinput data indicative of the plasma field and related vapor layercondition proximate electrode terminals 58.

Additionally, an electrosurgical probe sensor may measure electriccurrent at the distal end of probe 10, either for obtaining a currentvalue or to determine whether a treatment current has been initiated orstopped. Electric current data may similarly be transmitted tocontroller 104 for processing. Further, peak electric current and meanelectric current for a selected period, and peak electric current andRMS voltage for a selected period, may be measured by a sensorassociated with either probe 10 or power supply 28, and the measureddata input transmitted to controller 104 for processing as operatingparameter input data of interest.

In other embodiments, probe 10 may be used with a power supply 28capable of operating in more than one operating mode, such as anablation mode and a coagulation mode. In an ablation mode, power supply28 is adapted to provide a relatively high voltage output, in comparisonto operation in a coagulation mode, where power supply 28 may be adaptedto provide a relatively lower voltage output. In these embodiments,controller 104 may receive input data indicative of which mode powersupply 28 is operating. Specifically, a sensor (not shown) associatedwith power supply 28 may be provided to measure the voltage output ofpower supply 28, and then transmit such measurements indicating theoperating mode of power supply 28 to controller 104 in the form of inputdata for processing.

Responsive to the operating parameter input received by controller 104,a processor (not shown) associated with controller 104 preferablygenerates and sends control signals to suction pump 100. In certainembodiments, these control signals may operate to dynamically adjustfluid flow through suction pump 100, initiate fluid flow through suctionpump 100, delay initiating fluid flow through suction pump 100, ceasefluid flow through suction pump 100, decrease fluid flow through suctionpump 100, incrementally increase or decrease fluid flow through suctionpump 100, and/or maintain a particular fluid flow through suction pump100 if the operating parameters remain within a pre-selected valuerange. In other embodiments, the control signals from controller 104 maydynamically control the pressure at the suction pump 100.

Controller 104 may receive operating parameter input data indicating thestatus or operating condition of power supply 28. One such embodimentmay consist of controller 104 receiving input data as to whether powersupply 28 has been activated. Where power supply 28 has been activatedand probe 10 is in use, controller 104 may send signals that activatesuction pump 100 in response. Similarly, where power supply 28 has beendeactivated and probe 10 is not in use, controller 104 may send signalsthat deactivate suction pump 100. In a related embodiment, controller104 may receive operating parameter input indicative of the operatingmode of power supply 28. In response, controller 104 may initiate orcease fluid flow through suction pump 100. Specifically, controller 104may initiate fluid flow through suction pump 100 where power supply 28is detected to be operating in ablation mode, and cease fluid flowthrough suction pump 100 where power supply 28 is detected to beoperating in coagulation mode.

In certain additional embodiments, controller 104 may process input datarelative to conditions at the distal end of probe 10, and specificallyindicative of the condition of the plasma field and related vapor layercreated proximate electrode terminals 58. Suction pump 100 may bedeactivated when power supply 28 is initially activated, and theimpedance at the distal end of probe 10 may be monitored and measuredsuch that the data indicative of the operating condition of probe 10 maybe processed by controller 104. In some instances, when the impedance ismeasured to be at a desired level (indicating establishment of a stableplasma field and vapor layer at electrode terminals 58) or is measuredto exceed a specified threshold value, controller 104 may send a signalto suction pump 100 directing suction pump 100 to initiate fluid flow.Additional embodiments may consist of controller 104 sending signals tosuction pump 100 that direct suction pump 100 to modulate its speed inresponse to collected operating parameter input. For example, if adecrease in the impedance at the distal end of probe 10 is measuredduring operation, controller 104 may send a signal to suction pump 100directing it to decrease speed, thereby reducing fluid flow therethroughand at the treatment site. Conversely, if an increase of the impedanceat the distal end of probe 10 is measured during operation, controller104 may send a signal to suction pump 100 directing it to increasespeed, thereby increasing fluid flow therethrough.

Suction lumen 102 is preferably in communication within a suction lumenformed within probe 10 (e.g., fluid transport lumen 57 shown in FIGS. 2Aand 2B) and having a suction opening positioned proximate to thetreatment surface of the electrosurgical device. In alternateembodiments the suction lumen may attached to the exterior of theelectrosurgical device.

Referring to FIGS. 2A and 2B, the electrically isolated electrodeterminals 58 are spaced-apart over an electrode array surface 82. Theelectrode array surface 82 and individual electrode terminals 58 willusually have dimensions within the ranges set forth above. In thepreferred embodiment, the electrode array surface 82 has a circularcross-sectional shape with a diameter D (FIG. 2B) in the range from 0.3mm to 10 mm. Electrode array surface 82 may also have an oval shape,having a length L in the range of 1 mm to 20 mm and a width W in therange from 0.3 mm to 7 mm, as shown in FIG. 5. The individual electrodeterminals 58 will protrude over the electrode array surface 82 by adistance (H) from 0 mm to 2 mm, preferably from 0 mm to 1 mm (see FIG.3).

It should be noted that the electrode terminals may be flush with theelectrode array surface 82, or the terminals may be recessed from thesurface. For example, in dermatological procedures, the electrodeterminals 58 may be recessed by a distance from 0.01 mm to 1 mm,preferably 0.01 mm to 0.2 mm. In one embodiment of the invention, theelectrode terminals are axially adjustable relative to the electrodearray surface 82 so that the surgeon can adjust the distance between thesurface and the electrode terminals.

The electrode terminals 58 are preferably composed of a refractory,electrically conductive metal or alloy, such as platinum, titanium,tantalum, tungsten and the like. As shown in FIG. 2B, the electrodeterminals 58 are anchored in a support matrix 48 of suitable insulatingmaterial (e.g., ceramic or glass material, such as alumina, zirconia andthe like) which could be formed at the time of manufacture in a flat,hemispherical or other shape according to the requirements of aparticular procedure. The preferred support matrix material is alumina,available from Kyocera Industrial Ceramics Corporation, Elkgrove, Ill.,because of its high thermal conductivity, good electrically insulativeproperties, high flexural modulus, resistance to carbon tracking,biocompatibility, and high melting point.

As shown in FIG. 2A, the support matrix 48 is adhesively joined to atubular support member 78 that extends most or all of the distancebetween matrix 48 and the proximal end of probe 10. Tubular member 78preferably comprises an electrically insulating material, such as anepoxy, injection moldable plastic or silicone-based material. In apreferred construction technique, electrode terminals 58 extend throughpre-formed openings in the support matrix 48 so that they protrude aboveelectrode array surface 82 by the desired distance H (FIG. 3). Theelectrodes may then be bonded to the distal surface 82 of support matrix48, typically by an inorganic sealing material 80. Sealing material 80is selected to provide effective electrical insulation, and goodadhesion to both the ceramic matrix 48 and the platinum or titaniumelectrode terminals. Sealing material 80 additionally should have acompatible thermal expansion coefficient and a melting point well belowthat of platinum or titanium and alumina or zirconia, typically being aglass or glass ceramic.

In the embodiment shown in FIGS. 2A and 2B, probe 10 includes a returnelectrode 56 for completing the current path between electrode terminals58 and power supply 28. Return electrode 56 is preferably an annularmember positioned around the exterior of shaft 13 of probe 10. Returnelectrode 56 may fully or partially circumscribe tubular support member78 to form an annular gap 54 therebetween for flow of electricallyconducting liquid 50 therethrough. Gap 54 preferably has a width in therange of 0.15 mm to 4 mm. Return electrode 56 extends from the proximalend of probe 10, where it is suitably connected to power supply 28 viaconnectors 19, 20, to a point slightly proximal of electrode arraysurface 82, typically about 0.5 to 10 mm and more preferably about 1 to10 mm.

Return electrode 56 is disposed within an electrically insulative jacket18, which is typically formed as one or more electrically insulativesheaths or coatings, such as polytetrafluoroethylene, polyimide, and thelike. The provision of the electrically insulative jacket 18 over returnelectrode 56 prevents direct electrical contact between return electrode56 and any adjacent body structure or the surgeon. Such directelectrical contact between a body structure (e.g., tendon) and anexposed common electrode member 56 could result in unwanted heating andnecrosis of the structure at the point of contact causing necrosis.

Return electrode 56 is preferably formed from an electrically conductivematerial, usually metal, which is selected from the group consisting ofstainless steel alloys, platinum or its alloys, titanium or its alloys,molybdenum or its alloys, and nickel or its alloys. The return electrode56 may be composed of the same metal or alloy which forms the electrodeterminals 58 to minimize any potential for corrosion or the generationof electrochemical potentials due to the presence of dissimilar metalscontained within an electrically conductive fluid 50, such as isotonicsaline (discussed in greater detail below).

As shown in FIG. 2A, return electrode 56 is not directly connected toelectrode terminals 58. To complete this current path so that terminals58 are electrically connected to return electrode 56 via target tissue52, electrically conducting liquid 50 (e.g., isotonic saline) is causedto flow along liquid paths 83. A liquid path 83 is formed by annular gap54 between outer return electrode 56 and tubular support member 78. Anadditional fluid transport lumen 57 within an inner tubular member 59 isprovided to communicate with a fluid transport apparatus or suctionsource (such as suction pump 100) via suction lumen 102 and to removetissue and other material from the treatment site. In some embodiments,fluid transport lumen 57 may optionally be used to supply conductivefluid to a treatment site.

When a voltage difference is applied between electrode array 12 andreturn electrode 56, high electric field intensities will be generatedat the distal tips of terminals 58 with current flow from array 12through the target tissue to the return electrode, the high electricfield intensities causing ablation of tissue 52 in zone 88. Operatingparameters of power supply 28 or probe 10 are preferably monitored bycontroller 104 during operation thereof and suction is applied viasuction pump 100 at a desired flow rate and/or pressure to remove theablated tissue and other material from the treatment site in order tomaintain stable plasma field and associated vapor layer conditions.

FIG. 3 illustrates another embodiment of probe 10 where the distalportion of shaft 13 is bent so that electrode terminals extendtransversely to the shaft. Preferably, the distal portion of shaft 13 isperpendicular to the rest of the shaft so that electrode surface 82 isgenerally parallel to the shaft axis, as shown in FIG. 3. In thisembodiment, return electrode 55 is mounted to the outer surface of shaft13 and is covered with an electrically insulating jacket 18. Theelectrically conducting fluid 50 flows along flow path 83 through returnelectrode 55 and exits the distal end of electrode 55 at a pointproximal of electrode surface 82. The fluid is directed exterior ofshaft to electrode surface 82 to create a return current path fromelectrode terminals 58, through target tissue 52, to return electrode55, as shown by current flux lines 60 and then removed via transportlumen 57.

FIG. 4 illustrates an embodiment of the invention where electrosurgicalsystem 11 further includes a separate liquid supply instrument 64 forsupplying electrically conducting fluid 50 between electrode terminals58 and return electrode 55. Liquid supply instrument 64 comprises aninner tubular member or return electrode 55 surrounded by anelectrically insulating jacket 18. Return electrode 55 defines an innerpassage 83 for flow of fluid 50. As shown in FIG. 4, the distal portionof instrument 64 is preferably bent so that liquid 50 is discharged atan angle with respect to instrument 64. This allows the surgical team toposition liquid supply instrument 64 adjacent electrode surface 82 withthe proximal portion of supply instrument 64 oriented at a similar angleto probe 10. Transport lumen 57 may preferably be used in conjunctionwith a suction pump and controller to remove ablated tissue from atreatment site at a desired flow rate according to operating parametersindicative of conditions at the distal portion of probe 10.

FIG. 5 illustrates an embodiment of a probe 10 according to the presentinvention comprising a single active electrode 58 having a tubulargeometry. As described above, the return electrode may be an outertubular member 56 that circumscribes insulated conductor 42 and adhesivebonding material 79 which, in turn, adhesively joins to active electrodesupport members 48 a and 48 b. Electrode support members 48 a and 48 bmay be ceramic, glass ceramic or other electrically insulating materialwhich resists carbon or arc tracking. A preferred electrode supportmember material is alumina. In the example embodiment, alumina forms aninner portion 48 b of electrode support member 48 and a hollow tube ofalumina forms an outer portion 48 a of electrode support member 48.Fluid transport lumen 57 is provided in the interior of inner portion 48b. Tubular or ring-shaped active electrode 58 may be fabricated usingshaped cylinder of this metal comprising an electrically conductivemetal, such as platinum, tantalum, tungsten, molybdenum, columbium oralloys thereof. Active electrode 58 is connected to connector 19 (seeFIG. 2C) via an insulated lead 108. An electrically insulating jacket 18surrounds tubular member 56 and may be spaced from member 56 by aplurality of longitudinal ribs 96 to define an annular gap 54therebetween (FIG. 22). Annular gap 54 preferably has a width in therange of 0.15 to 4 mm. Ribs 96 can be formed on either jacket 18 ortubular member 56. The distal end of the return electrode 56 is adistance L1 from electrode support surface 82. Distance L1 is preferablyabout 0.5 mm to 10 mm and more preferably about 1 to 10 mm. The lengthL1 of return electrode 56 will generally depend on the electricalconductivity of the irrigant solution.

The configuration depicted in FIG. 5 may be used with the integralsupply means and return electrodes described above. Alternatively, theseprobe configuration of FIG. 5 may be operated in body cavities alreadycontaining an electrically conducting liquid, obviating the need foreither an integral supply of said liquid or an electrically insulatingsleeve to form a conduit for supply of the electrically conductingliquid 50. Instead, an electrically insulating covering may be appliedto substantially all of the return electrode 56 (other than the proximalportion).

Referring now to FIGS. 6A-6C, an alternative embodiment incorporating ametal screen 610 electrode is illustrated. As shown, metal screen 610has a plurality of peripheral openings 612 for receiving electrodeterminals 1040, and a plurality of inner openings 614 for allowingaspiration of fluid and tissue through opening 609 of the fluidtransport lumen. As shown, screen 610 is press fitted over electrodeterminals 1040 and then adhered to shaft 1000 of probe 10. In alternateembodiments, metal screen 610 may comprise a mesh-type configuration andmay further comprise a variety of conductive metals, such as titanium,tantalum, steel, stainless steel, tungsten, copper, gold or the like.

In one embodiment, during operation of an electrosurgical systemutilizing a screen-type electrode, one or more operating parameters maybe monitored to determine whether metal screen electrode 610 has becomeobstructed. Responsive to detecting that screen electrode 610 isobstructed, controller 104 may reverse the flow of suction pump 100 inorder to clear the obstruction from screen electrode 610. The monitoredoperating parameter may include, for instance, pressure within the fluidtransport lumen 57.

Now referring to FIG. 7, a schematic diagram of a controller of the typeutilized in the present invention is shown. Controller 700 includes atleast one input port 710 and at least one output port 714. Controller700 preferably receives input from sensors (not expressly shown) withina power supply (such as power supply 28), from a suction lumen (such asfluid transport lumen 57), and/or from an electrosurgical probe (such asprobe 10) relating to one or more operating parameters. In a preferredembodiment, the operating parameters may include one or more of thefollowing: impedance, electric current (including whether a treatmentcurrent has been initiated or stopped), peak electric current and meanelectric current for a selected period, peak electric current and RMSvoltage for a selected period. In related embodiments, the operatingparameters may include any operating parameters indicative of operatingconditions at the treatment surface of the electrosurgical probe and inparticular may include operating parameters indicative of the conditionof the plasma field or the quality of the vapor layer created proximatethe treatment surface. For devices that may operate in more than oneoperating mode, such as an ablation mode and a coagulation mode, theoperating parameter may alternatively include data indicative of theoperating mode of the device.

Operating parameter input data indicative of conditions associated withthe system received at port 710 is processed by processor 712. Processor712 may encompass any suitable hardware and software, includingcontrolling logic, necessary to receive the input data and generatedesired output commands to provide to a suction source (such as suctionpump 100). Output commands generated by processor 712 are sent to asuction source electrically coupled to controller 700 via output port714. In a preferred embodiment, the output commands generated byprocessor 712 may include, but are not limited to: dynamically adjustfluid flow through the suction source, initiating fluid flow through thesuction source, delay initiating fluid flow through the suction source,ceasing fluid flow through the suction source, decreasing fluid flowthrough the suction source, incrementally increasing or decreasing fluidflow through the vacuum source, and/or maintain a particular fluid flowthrough the suction source if the operating parameters remain within apre-selected value range. In other embodiments, the control signals fromcontroller 700 may dynamically control the pressure at the suction pump.Controller 700 may be a stand-alone device or may be incorporated in apower supply, a suction pump, an electrosurgical device or anycombination thereof.

Now referring to FIG. 8, a schematic diagram of an electrosurgicalsystem 800 according to teachings of the present disclosure is shown.Electrosurgical system 800 includes electrosurgical probe 810 which maybe any monopolar, bipolar or plasma-based electrosurgical device asdiscussed above. Probe 810 is in communication with power supply 812 viacable 830 and suction source 814 via suction lumen 834. Optionally, avalve 824 (such as, for example, a pinch valve or other suitable valve)may be provided along suction lumen 834. Controller 816 is incommunication with power supply 812 via cable 832 and with suctionsource 814 via cable 836. Controller 816 is also shown in communicationwith sensor 820 associated with probe 810, and in communication withvalve 824.

Probe sensor 820 is adapted to monitor one or more operating parametersassociated with electrosurgical probe 810. Sensor 822 may be associatedwith power supply 812 and accordingly in communication with controller816, and is adapted to monitor one or more operating parameters relatedto power supply 812. In alternate embodiments an additional sensor (notexpressly shown) may be provided in association with suction lumen 834to monitor pressure therein and further to be in communication withcontroller 816.

In operation, input signals containing one or more selected operatingparameters of electrosurgical probe 810 and/or power supply 812 (asdiscussed above) are preferably sent to controller 816 when probe 810and power supply 812 are in use. The input signals may be sent fromeither or both power supply 812, probe 810 or sensors associatedtherewith (i.e., sensor 820 with respect to probe 810, and sensor 822with respect to power supply 812). In response to the input signalsreceived, controller 816 may process the data based on the selectedoperating parameter. Controller 816 may then preferably generate suctionsource control commands, as discussed above, in response to the receivedoperating parameter input. Controller 816 may then send such suctioncontrol commands to suction source 814 via cable 836 to dynamicallycontrol suction through lumen 834. In some embodiments, controller 816may optionally send a control signal to valve device 824 to open orclose valve 824. In one alternative embodiment, controller 816 maycommunicate with probe 810, power supply 812, valve 824 and/or suctionsource 814 wirelessly.

Although the disclosed embodiments have been described in detail, itshould be understood that various changes, substitutions and alterationscan be made to the embodiments without departing from their spirit andscope.

1-31. (canceled)
 32. A system for electrosurgically treating tissuecomprising: an electrosurgical probe having a distal end including atleast one active electrode and a fluid transport lumen having an openingproximate the active electrode; a power supply electrically coupled tothe at least one active electrode and adapted to provide a highfrequency voltage to the at least one active electrode; a suction pumpfluidly connected to the fluid transport lumen; at least one sensoradapted to measure at least one operating parameter indicative of anoperating condition proximate the at least one active electrode; and acontroller in communication with the at least one sensor and incommunication with the suction pump, the controller adapted to controlthe suction pump based on the at least one operating parameter.
 33. Thesystem of claim 32, wherein the at least one sensor is associated withthe electrosurgical probe.
 34. The system of claim 32, wherein the atleast one sensor is disposed proximate the power supply.
 35. The systemof claim 32, wherein the at least one sensor is disposed proximate thefluid transport lumen.
 36. The system of claim 32, wherein thecontroller receives data from the at least one sensor indicative of aplasma field condition proximate the at least one active electrode. 37.The system of claim 32, wherein the at least one sensor provides outputto the controller indicative of a vapor layer stability proximate the atleast one active electrode.
 38. The system of claim 32, wherein thecontroller is adapted to adjust a fluid flow through the fluid transportlumen based on signals received from the at least one sensor.
 39. Thesystem of claim 32 wherein the at least one operating parametercomprises impedance.
 40. The system of claim 32 wherein the at least oneoperating parameter comprises suction pressure.
 41. The system of claim32, wherein: the power supply is adapted to provide a first highfrequency voltage in a first operating mode and a second high frequencyvoltage in a second operating mode; and at least one operating parameteris indicative of the first operating mode or the second operating mode.42. The system of claim 41, wherein the first operating mode comprisesan ablation mode, and the second operating mode comprises a coagulationmode.
 43. The system of claim 32, wherein the controller is adapted todynamically adjust the suction pump.
 44. The system of claim 32, thecontroller further comprising: an input port for receiving an inputindicative of the at least one operating parameter; a processor adaptedto determine a fluid flow for the suction pump responsive to the atleast one operating parameter; and an output port for sending an outputsignal to the suction pump.
 45. A system for electrosurgically treatingtissue comprising: an electrosurgical probe having at least one activeelectrode; a fluid transport lumen having an opening proximate the atleast one active electrode; a power supply electrically coupled to theat least one active electrode and adapted to provide a high frequencyvoltage to the at least one active electrode; a suction pump fluidlyconnected to the fluid transport lumen; at least one sensor adapted tosend output signals indicative of at least one operating parameterassociated with the system; and a controller communicatively coupled tothe at least one sensor and the suction pump and wherein the controlleris adapted to receive the output signals from the at least one sensorand send control signals to the suction pump based on the sensor outputsignals.
 46. The system of claim 45, wherein the controller is adaptedto receive output signals indicative of operating conditions adjacentthe at least one active electrode.
 47. The system of claim 45, whereinthe controller is adapted to receive output signals indicative of aplasma field condition adjacent the at least one active electrode. 48.The system of claim 45, wherein the at least one sensor provides outputsignals to the controller indicative of a vapor layer stabilityproximate the at least one active electrode.
 49. The system of claim 45,wherein the controller further comprises a processor adapted todetermine a fluid flow for the suction pump responsive to the at leastone operating parameter.